The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
The determination of vehicle mass is important to the efficient operation of today's vehicles, especially in highly efficient light and heavy duty trucks, increasingly capable autonomous driving vehicles, and continuously developed electric powered vehicles. For example, vehicle mass is an input consideration for algorithms for proper gear changing control in a transmission having staged gears or motor torque output control for an electric powered vehicle. Vehicle mass may also be used by various vehicle controllers in anti-lock brake systems, intelligent vehicle/highway systems and fleet management systems, to name a few. In addition, vehicle mass can be useful in speed control systems, such as for use with an active speed control system. One problem with using vehicle mass estimation as a control parameter is that it varies with vehicle loading and configuration and is usually difficult to predict with minimal error. For example, the mass of a medium sized sedan can increase several hundred pounds when going from zero passengers to having a full capacity vehicle. Adding four passengers at 150 lbs. each is a total of 600 lbs. which can add approximately 25% to the weight of the vehicle. This can cause significant differences between the best operating parameters for the vehicle and how the vehicle is actually operated.
Because the mass of a particular vehicle may vary greatly, a means for accurately estimating actual vehicle mass when the vehicle is in operation is required if the dynamic vehicle mass is to be used as a control parameter. Thus, if the mass parameter is fixed at a particular value in the control system, then the various control features described above will not allow for optimal vehicle performance under all types of load, road, and driving conditions.
Vehicle acceleration is typically measured by an accelerometer in the vehicle. However, one of the problems associated with the collection of speed data is that speed signal is typically very noisy. When vehicle acceleration is used to estimate the vehicle mass, the noise problem is even more significant. In order to determine acceleration, it is often necessary to measure the increase or decrease in speed values at very close time intervals. This differentiation in speed values at close time intervals causes the acceleration signal to be buried in the noise of the speed signal. Inaccurate determinations of vehicle acceleration and a correspondingly inaccurate determination of vehicle mass may result. The various controllers relying on an accurate vehicle mass determination may in turn perform ineffectively and inefficiently.
What is therefore needed is a technique for estimating vehicle mass that addresses the foregoing shortcomings as well as other deficiencies. Such a technique should provide reliable, more accurate estimates of vehicle mass. The technique should also be inexpensive to implement, and be readily integrated into existing vehicle control systems.